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=============================================================================
FreeBSD-EN-19:11.net                                            Errata Notice
                                                          The FreeBSD Project

Topic:          Incorrect locking in networking stack

Category:       core
Module:         net
Announced:      2019-06-19
Affects:        FreeBSD 12.x
Corrected:      2019-04-01 14:19:09 UTC (stable/12, 12.0-STABLE)
                2019-06-19 16:41:18 UTC (releng/12.0, 12.0-RELEASE-p6)

For general information regarding FreeBSD Errata Notices and Security
Advisories, including descriptions of the fields above, security
branches, and the following sections, please visit
<URL:https://security.FreeBSD.org/>.

I.   Background

Some parts of the network stack use a synchronization primitive, epoch(9),
that is new in FreeBSD 12.0.  In some places where reader-writer locks were
previously used, existing KPIs were preserved and their implementations
replaced with epoch(9).

II.  Problem Description

A pair of KPIs that were converted to epoch(9) were modified incorrectly, and
thus failed to provide the synchronization guarantees expected by their
consumers.

III. Impact

The bug can cause kernel memory corruption or kernel assertion failures,
depending on whether the INVARIANTS option is configured.  The bug is more
likely to impact heavily loaded systems.

IV.  Workaround

No workaround is available.

V.   Solution

Upgrade your system to a supported FreeBSD stable or release / security
branch (releng) dated after the correction date.

Perform one of the following:

1) Update your system via a binary patch:

Systems running a RELEASE version of FreeBSD on the i386 or amd64
platforms can be updated via the freebsd-update(8) utility:

# freebsd-update fetch
# freebsd-update install

Afterwards, reboot the system.

2) Update your system via a source code patch:

The following patches have been verified to apply to the applicable
FreeBSD release branches.

a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.

# fetch https://security.FreeBSD.org/patches/EN-19:11/net.patch
# fetch https://security.FreeBSD.org/patches/EN-19:11/net.patch.asc
# gpg --verify net.patch.asc

b) Apply the patch.  Execute the following commands as root:

# cd /usr/src
# patch < /path/to/patch

c) Recompile your kernel as described in
<URL:https://www.FreeBSD.org/handbook/kernelconfig.html> and reboot the
system.

VI.  Correction details

The following list contains the correction revision numbers for each
affected branch.

Branch/path                                                      Revision
- -------------------------------------------------------------------------
stable/12/                                                        r345764
releng/12.0/                                                      r349198
- -------------------------------------------------------------------------

To see which files were modified by a particular revision, run the
following command, replacing NNNNNN with the revision number, on a
machine with Subversion installed:

# svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base

Or visit the following URL, replacing NNNNNN with the revision number:

<URL:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>

VII. References

<URL:https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=236846>

The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-EN-19:11.net.asc>
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